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Lampbrush Chromosomes

Lampbrush Chromosomes

In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops...

Lampbrush Chromosomes

Lampbrush Chromosomes

Chromosomal Theory of Inheritance

Chromosomal Theory of Inheritance

In 1866, Gregor Mendel published the results of his pea plant breeding experiments, providing evidence for predictable patterns in the inheritance of physical characteristics. The significance of his findings was not immediately recognized. In fact, the existence of genes was unknown at the time. Mendel referred to hereditary units as “factors.”

Polytene Chromosomes

Polytene Chromosomes

Polytene chromosomes are giant interphase chromosomes with several DNA strands placed side by side. They were discovered in the year 1881 by Balbiani in salivary glands, intestine, muscles, malpighian tubules, and hypoderm of larvae Chironomus plumosus. Hence, these are also called "Salivary gland chromosomes." These are found in insects of the order Diptera and Collembola; in certain organs of mammals; and synergids, antipodes of flowering plants. Polytene chromosomes are also...

Chromosome Structure

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA sequence that links sister chromatids. This is also where kinetochores, protein complexes to which spindle microtubules attach, are constructed after the chromosome is replicated. The kinetochores allow the spindle microtubules to move the chromosomes within the cell during cell division.
Telomeres consist of non-coding repetitive nucleotide...

Chromosome Structure

Chromosome Structure

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Related Experiment Video

Updated: Jan 22, 2026

In Vitro Model of Human Cutaneous Hypertrophic Scarring using Macromolecular Crowding

In Vitro Model of Human Cutaneous Hypertrophic Scarring using Macromolecular Crowding

Published on: May 1, 2020

Chromosome Organization: Making Room in a Crowd.

Handuo Shi¹, Kerwyn Casey Huang²

¹Department of Bioengineering, Stanford University, Stanford, CA 94305, USA.

Current Biology : CB

|July 10, 2019

Summary

Prokaryotic cells organize DNA without membranes. Large biomolecules in DNA-free regions exclude DNA through entropic forces, explaining cellular organization.

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Last Updated: Jan 22, 2026

In Vitro Model of Human Cutaneous Hypertrophic Scarring using Macromolecular Crowding

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Micromanipulation of Chromosomes in Insect Spermatocytes

Micromanipulation of Chromosomes in Insect Spermatocytes

Published on: October 22, 2018

Area of Science:

Cell Biology
Molecular Biology
Biophysics

Background:

Prokaryotic cells, despite lacking membrane-bound organelles, exhibit organized internal structures.
The nucleoid, the region containing genetic material in prokaryotes, is spatially organized within the cell.
Understanding the mechanisms of prokaryotic cellular organization is crucial for comprehending fundamental life processes.

Purpose of the Study:

To investigate the spatial organization of the nucleoid in prokaryotic cells.
To identify the components and mechanisms responsible for DNA segregation and cellular compartmentalization.
To elucidate the role of non-DNA components in structuring the prokaryotic cell.

Main Methods:

Utilized advanced microscopy techniques to visualize subcellular structures in prokaryotes.
Employed biochemical assays to identify the molecular composition of DNA-free regions.
Applied biophysical modeling to understand the forces governing molecular interactions and spatial organization.

Main Results:

Demonstrated that DNA-free regions within prokaryotes are densely populated with large biomolecules.
Showed that these large biomolecules exclude DNA from specific cellular compartments.
Identified entropic forces as the primary mechanism driving this DNA exclusion and nucleoid organization.

Conclusions:

The spatial organization of the prokaryotic nucleoid is achieved through the physical exclusion of DNA by large biomolecules.
Entropic forces play a significant role in establishing and maintaining subcellular compartmentalization in prokaryotes.
This mechanism provides a novel perspective on genome organization in the absence of membrane-bound organelles.